Rebreathers and proper profiles

[Grisha]

I'm about to jump into the world of rebreathers, but if there's anything technical diving has taught me, it's "do your research until every theory is second nature" and one particular thing that is bugging me was an offhand comment made by another instructor along the lines of "not leaning forward as to avoid a caustic cocktail" (paraphrasing). Does this mean that water may pool in the counter-lung in such a way that if you lean forward, it would come into contact with your scrubbers and partially dissolve them, leading to a caustic cocktail scenario? Or do I just have an overactive imagination?

 

[northernone]

Depending specifically in the rebreather design it's worth remembering.

I've had a partial flood on a home build and when tipping forward to go under a log the change in posture caused me to pour the slurry into my loop.

Flooding a loop shouldn't be common nor should the regular moisture and lung butter that collects be caustic.

Regards,
Cameron

 

[Grisha]

Thank you very much for the input. I'll be sure to take it into account when deciding on a rebreather model.

 

[JohnnyC]

Does said instructor dive a rebreather? He (or she) is painting a pretty broad stroke considering it's the rebreather design that will dictate any forward movement of liquid into ones face hole.....

 

[Kristi@CCDS]

This really depends on a few variables... for one, the design of the canister and counter lungs, the water trapping ability of the unit, and the flood tolerance. Units vary. I always suggest doing try dives on the units of interest if at all possible. A try dive longer than an hour is preferable since you really won't get a great idea for the differences between units without spending a little bit of time on each. It's worthwhile to pay for a private try session if possible to get this kind of experience before jumping into a (in most cases) $8k + investment.

 

[Gareth J]

As has been said, a caustic cocktail is a 'risk', mixing water with sofnolime will produce a caustic cocktail.

Under normal operating circumstances this should not happen.
The risk is when you have a loop flood. Again, this is dependent on the 'flood tolerance' of the unit. There are additional issues when you have a loop flood, this includes increased breathing resistance, compromising the sofnolime (which increases the risk of breakthrough), etc.
'If' you flood the loop you can consider bailing out and going back onto OC.

MOD1, the recommendation is to bailout under all adverse circumstances, unit failures or warnings. It is only after MOD2 that you consider staying on the loop in the event of an issue, this is based on experience, and analysis of the fault.

I have been diving an Inspiration for a very long time. Over this period, I have never had enough water in the loop to cause an issue. The Inspiration is noted for being exceptionally flood tolerant. - Not that I have any intention on proving this!

Gareth